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Discussion Starter · #1 ·
My right carb is acting up and running lean. I've rebuilt this carb and when I put it on my bike and opened the petcock, fuel began seeping out the side of the carb. I JB welded the side as a band aide until I buy a new replacement carb. Apparently the crack was worse than I thought. I'm pretty sure the previous owner had junk gas in it and possibly froze in the winter and cracked the body, but I could be wrong.

On PG 58 on this link there's a sectional view of the carb.

https://drive.google.com/file/d/0B8RLEMngUB63VVBENlJuTEhyeW8/edit

When I tested the carb at work there was Popping and backfiring like crazy on just the right side. the left carb works beautifully. I put my thumb over the part marked "AJ" on that link and my problem went away. What is that port used for????
 

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That is the air correction jet. When you plug it the idle mixture is richened up. The carb is too lean at idle, a plugged jet or an air leak is probably the cause.
 
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Discussion Starter · #3 ·
my shop foreman said there's a way to try and clean it out by whopping on the throttle real quick and quickly putting your hand over the carb. that the pull from the motor pulls the trash out. he tried it on my bike but it didn't work. I left it at work so I'll have to check the jets on Monday. The screen in the petcock doesn't stop trash?
 

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It'll stop the "large particulate" but not necessarily the "fine stuff". the finer particulate would likely block your carb jets (it there even is any in your tank). Is your tank clean on the inside?

You said the PO left bad gas in the carb - your problem is likely that turned to varnish and is contributing to clogging your jets.

My advice: don't look for the "quick fix" - you'll never be happy with the results. Take the carbs off, bath them in a sonic cleaner (purple Simple Green is great) or carb cleaner bath, and clean them with a fine guitar string and compressed air. Reinstall, and see if your problem persists.
 

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Discussion Starter · #5 ·
I rebuilt the carbs. they sat in carb cleaner for 24 hrs and I used our parts cleaner at work to rinse them thoroughly and used the shop's pressure to blow out the channels. I did clean my tank before and actually soaked it in metal rescue. I'm a tech for Hyundai so I see people getting trash in their gas all the time, so I'm not ruling that out. I was stuck on Thursday and needed gas and put ethanol in it which I hated to do but hate pushing even more. If there's trash in my tank the bowls will have debris. I'm gonna take the bowls off tomorrow and see whats what.
 

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Discussion Starter · #6 ·
tomorrow I'm doing a leak-down test and compression test to try and rule out valves. GOD I hope its not a valve issue. I'm pretty sure I have a crack somewhere in the carb itself
 

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Discussion Starter · #7 ·
SO I've pretty much torn the bike down completely. My tank has been lifted up so I can double check all my wiring connections, the cover for the points is off, and my carbs are off. I have new Dynatec coils with condenser along with new wires and plugs. I also have new points on.

-My timing marks for the advance timing gear are where they need to be (I'm not 180 deg out)
-My gap for my points is at .014
-My carbs have been rebuilt and cleaned up
-I checked for valve clearance and I'm at the recommended. (I'm lucky enough to still have the factory tool kit and it has the feeler gauge needed)

When I whop on the throttle I get a lot of popping, backfiring, and bogging. I've tried messing with advancing and retarding it but it still wont run right. How do you check the vacuum piston? I found a set of carbs on ebay from a company that restores bikes, but I'm wondering if its worth the $120 for the set
 

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I guess the first question is, are the carbs synced?

When you rebuilt the carbs did you install new O-rings?

My only experience with backfiring has always been timing. Try to set them using this method, I find it easier and better ( at least for me ).
 

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Discussion Starter · #9 ·
thanks for the link. Yea I used that when I was doing the timing. Common Motors has been awesome throughout my build. This wound up being a few different problems. I don't think I mentioned in this thread that my bike sat for 42 years. Well, a few parts on the right carb (problem side) were seeping fuel. I did a band aide fix just to see if the bike would run and use that to judge whether or not I would sink money into it and how much I would be willing to do.

Well! APPARENTLY there's a vent on the right side of the carbs for the bowl. When I JB welded I accidentally plugged that. I never found that vent on any diagrams and I thought the overflow was the vent for the bowl. Never in a million years would have guessed there was TWO vents for the bowls! The bowl was venting enough to allow fuel to fill it at an idle, but only at an idle. Pretty much, the bowl couldn't fill fast enough for demand.... Thus my problem running lean. My second problem was dirty connectors from the points to the condenser/coils.

If I remember later I'll post a pic of said vents. They're pretty small and easy to miss on the right side in front of the fuel line.
 

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thanks for the link. Yea I used that when I was doing the timing. Common Motors has been awesome throughout my build. This wound up being a few different problems. I don't think I mentioned in this thread that my bike sat for 42 years. Well, a few parts on the right carb (problem side) were seeping fuel. I did a band aide fix just to see if the bike would run and use that to judge whether or not I would sink money into it and how much I would be willing to do.

Well! APPARENTLY there's a vent on the right side of the carbs for the bowl. When I JB welded I accidentally plugged that. I never found that vent on any diagrams and I thought the overflow was the vent for the bowl. Never in a million years would have guessed there was TWO vents for the bowls! The bowl was venting enough to allow fuel to fill it at an idle, but only at an idle. Pretty much, the bowl couldn't fill fast enough for demand.... Thus my problem running lean. My second problem was dirty connectors from the points to the condenser/coils.

If I remember later I'll post a pic of said vents. They're pretty small and easy to miss on the right side in front of the fuel line.
I was going to mention the connectors, completely forgot to suggest that as I've experienced that as a problem as well.

Whats your carb serial number? I might have an extra one laying around if your interested.
 

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Discussion Starter · #11 ·
I was actually debating an upgrade if I was going to replace carbs. I haven't done any research into it so I'm not sure if there is any carbs out there that are better. Mine are stamped "14H" by the air cleaner.
 
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